There might be two reasons for that:
1- either your clock is set to UTC (local time) and your config believe it is set to local time (UTC)
2- or your /etc/zoneinfo symlink does not point to your correct local zone file.
The symptom for that is that each time you reboot from MacOS to Linux your clock is drifted by a fixed amount of hours.

Remedies:
1- check that /etc/zoneinfo points to the correct zone file (usr/share/zoneinfo/Europe/Zurich in my case)
2- try to change the CLOCK setting in /etc/rc.conf to either CLOCK="UTC" or CLOCK="local".